Both human-operated and autonomous vehicles may be used to provide transportation services. A user may arrange for a vehicle to pick up the user at a specified location. However, the user may not recognize the vehicle and/or the vehicle (or operator thereof) may not recognize the user. Likewise, the user and/or vehicle (or operator thereof) may have a general specification of the other's location, e.g., a parking lot, a given city block, etc., but may lack further ability to identify the other's location, and to complete a rendezvous. Such issues are not limited to, but can pertain particularly, to crowded or congested areas such as transportation hubs or venues where numerous users are looking to identify a pick up vehicle which may be in long lines of awaiting vehicles; current approaches to visual or other sensor identification, for example, can be insufficient. Moreover, there are problems with existing communications between user devices and vehicle computing devices. For example, communications via a network, such as a cellular network or the like, can be subject to latency and/or otherwise generally unreliable. Other existing communications mechanisms, especially RF (radio frequency) communications carried out by protocols such as BLUETOOTH® and the like, can be difficult to establish and/or otherwise unreliable. In addition, especially when finer resolutions are called for, Global Positioning System (GPS) technology may prove unreliable or inaccurate.